Objective：To search for a method for analyzing medical service quality of different disease entities using the first page data of medical records. Methods： Based on documents review and real data analysis, the basic principles, methods and steps of disease entity dividing and selecting, evaluation index selecting, and calculating were introduced. Special attention was paid to certain problems in the discussion. Results： When the inpatients of selected disease entities covered 60%o of total hospitalized patients, the medical quality information included exceeded 80% of the total information. For 97.66% disease entities, their inpatient cost and length of hospital stay were logarithmic-normally distributed. Conclusion. Dividing disease entities by fixed digits of ICD-9 code is easily performable. This method should be used when the disease entities include about 60% of total inpatients, and geometric mean should be used in calculating average length of hospital stay and average cost.